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68 lines
1.2 KiB
Groff
68 lines
1.2 KiB
Groff
.\" Generated by Mmark Markdown Processer - mmark.miek.nl
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.TH "COREDNS-BUFSIZE" 7 "August 2020" "CoreDNS" "CoreDNS Plugins"
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.SH "NAME"
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.PP
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\fIbufsize\fP - sizes EDNS0 buffer size to prevent IP fragmentation.
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.SH "DESCRIPTION"
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.PP
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\fIbufsize\fP limits a requester's UDP payload size.
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It prevents IP fragmentation, mitigating certain DNS vulnerabilities.
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.SH "SYNTAX"
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.PP
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.RS
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.nf
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bufsize [SIZE]
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.fi
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.RE
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.PP
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\fB[SIZE]\fP is an int value for setting the buffer size.
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The default value is 512, and the value must be within 512 - 4096.
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Only one argument is acceptable, and it covers both IPv4 and IPv6.
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.SH "EXAMPLES"
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.PP
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Enable limiting the buffer size of outgoing query to the resolver (172.31.0.10):
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.PP
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.RS
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.nf
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\&. {
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bufsize 512
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forward . 172.31.0.10
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log
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}
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.fi
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.RE
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.PP
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Enable limiting the buffer size as an authoritative nameserver:
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.PP
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.RS
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.nf
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\&. {
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bufsize 512
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file db.example.org
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log
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}
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.fi
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.RE
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.SH "CONSIDERATIONS"
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.IP \(bu 4
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Setting 1232 bytes to bufsize may avoid fragmentation on the majority of networks in use today, but it depends on the MTU of the physical network links.
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.IP \(bu 4
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For now, if a client does not use EDNS, this plugin adds OPT RR.
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